The Roman Empire was the most successful the world had ever known.
At its peak, in the 2nd century AD, it covered five million square kilometres.
From Hadrian's Wall in the north,
to ancient Mesopotamia in the east.
All of it run by a system of remarkable efficiency and stability.
They called it Pax Romana, the Roman Peace,
and its benefits were enjoyed by 60 million people.
The Romans would proudly boast of having come up with the final word on civilisation.
Peace, security and prosperity, all underwritten by an imperial power with a civilising mission.
As long as you got with the programme, paid your taxes,
committed to the Empire and, of course, kept the peace, the benefits of civilisation would come to you.
What more could anyone want?
The answer was more than the Pax Romana could supply.
This mighty empire would endure some mad, bad and dangerous emperors.
But in the end, it would be subverted by an obscure religious cult from the East.
Its followers would reject, not just Rome
but all that Rome had come to mean in the story of civilisation.
The city of man would be eclipsed by the city of God.
Here's a rare thing in our story of the ancient world -
a massive, expensive public monument
dedicated not to some blood-soaked triumph over a cringing enemy,
but to that elusive, precious thing called peace.
Surely the greatest good that human civilisation can aspire to.
It was created at the behest of the man who established the Pax Romana.
Augustus, Rome's first Emperor.
This is the Ara Pacis, the Altar of Peace, built by Augustus in 13BC.
On this frieze here, it shows Augustus coming back from campaign,
the guarantor and author of peace.
Quite a transformation from the teenage warlord who reputedly ripped out the eyes of one of his enemies.
18 years earlier, plain old Octavian Caesar, as he was then,
was last man standing in the brutal civil wars which had torn the Roman Republic apart.
As victor, he'd faced a simple choice -
resuscitate the Republic ruled by the Senate and the people, or put it out of its misery.
But the canny Octavian, rebranded Augustus, found a third way.
He killed the Republic's soul, but kept its body alive.
On the frieze, we see Augustus with three main constituencies.
The first of these is the Senate.
Augustus was going to claim that he was going to restore the Roman Republic.
To do that, he needed to restore the dignity and authority of the Senate.
The second group are the priesthood.
Augustus was going to claim that he'd restore traditional Roman religion.
The third group is a real novelty.
We can see them up here.
Women and children.
These are members of Augustus's immediate family.
Augustus wanted to get the people of Rome used to a new concept.
An imperial dynasty.
As Augustus knew, Romans had a visceral hatred of kings.
To plant his dynasty firmly in this hostile soil,
Augustus had to master a tricky political manoeuvre.
A Roman writer would later define it as "getting higher by stepping down".
You can see what that meant in practice in another public monument
erected 30 years after the Altar of Peace.
The Res Gestae, literally The Things Done by Augustus,
is the carefully doctored CV of the man
who brought the principles of monarchy back to Rome after 500 years.
As a public testament, the Res Gestae is a very odd document indeed.
Most Roman aristocrats on their epitaphs would be boasting about
the honours and the offices that they had accrued, but the Res Gestae does the diametric opposite.
On it, Augustus boasts about the offices that he's turned down.
So up here, we've got, "The dictatorship which was offered
"to me in my absence and presence by the people and senate of Rome.
"I didn't take it. The Consulship offered to me annually and eternally. I didn't take it.
"The coronation crown that was offered to me. I didn't accept it."
One title that the self-denying Augustus did accept was Pater Patriae, Father of the Country.
He garnished it with a disingenuous little phrase
that added more smoke and mirrors to this monarchy in disguise.
Primus inter pares, or first amongst equals,
would remain the modus operandi for all emperors after Augustus.
Augustus would maintain the charade of visiting the senate house and seeking advice from its leaders
and even half the provinces would remain in senatorial control.
But they tended to be the ones that didn't have large standing armies.
Just in case.
The dead hand of the Father of the Country weighed heavily here in the Senate.
Woe betide the Senator who failed to do Augustus's bidding.
The habits of debate and dissent shrivelled and died.
Augustus lived long enough to see his imperial system take firm root.
But its resilience was tested by what came next.
A succession of rulers that gives the term Roman Emperor its lurid associations
with vanity...
debauchery...
and insanity.
This hall is literally full of emperors and, as you can see, they come in various shapes and sizes.
But one of the interesting things about the Empire is
that it often didn't seem to matter what the man at the top was like.
He could be mad, bad and dangerous, but the Empire just carried on regardless.
The machinery of empire - trade, tax collecting and public works - rarely missed a beat.
But the imperial system distorted the values and ideals of Rome.
For Rome's elite, life under an emperor was a form of exquisite torture.
The closer you got to the centre of power, the greater your chances of an untimely death.
Such unspoken inequalities often created embarrassing and even dangerous situations.
The Emperor Claudius, who often got things wrong,
used to turn up at senators' houses for dinner uninvited,
leaving his hosts to sit there quaking in their boots over dinner
as his bodyguards served up the food.
One obsequious senator threw himself at the feet of the aged Emperor Tiberius, knocking him over.
He almost ended up with a guardsman's sword in his guts.
Many senators embraced stoicism,
the cultivation of indifference in the face of life's trials and tribulations.
It was a psychological defence mechanism against these arbitrary and dangerous times.
Many of them decided to exercise the ultimate freedom
they still had left under a tyrant
and that was choosing the manner and time of their own deaths.
So there was a whole series of senatorial suicides,
including men who invited all of their friends to dinner, where they read poetry, ate something,
and then they went off to the baths where the guy who was going to commit suicide slashed his wrists.
But then in another twist, one of these guys had his hands bandaged up again.
He went out again, spent some time discussing things with his friends,
before going back in and having the bandages removed, where he bled to death.
While Rome's imperial system drove its elite to suicides,
the masses were encouraged to behave as spoilt brats.
The million-strong population of Rome was always one grievance away
from becoming a million-strong mob.
So smart emperors kept it sweet with panem et circenses -
bread and circuses.
The bread came first.
Augustus handed out a free monthly dole of grain
to 200,000 Romans, one-fifth of the city's population.
He could afford to be generous because Rome had acquired
the ancient world's great bread basket of North Africa.
The abundant fruits of empire helped fill the bellies of the Romans and kept them quiet.
There was a trading boom in the Mediterranean, unprecedented in the ancient world.
The ships headed to Rome laden with grain, building materials and amphora full of olive oil.
So much for the bread, but the plebs also demanded stronger meat.
The circuses.
The Roman games had gladiators, chariots and wild beasts.
These Las Vegas-scale spectaculars were paid for by the emperor or his representatives.
And death was always top of the bill.
In this murky, subterranean world, animals and men would wait
before they were taken up to the arena above to die for the entertainment of the crowds there.
The Roman Empire built on bread and circuses - cheap food and cheap thrills.
The grim theatre of death that played out on the sandy floor of the amphitheatre
was accompanied by cut-and-thrust of a more subtle kind.
The political interaction that took place between the crowd and their emperor.
There were ways of doing it and ways of not doing it.
Tiberius got it completely wrong and came across as being very aloof because he didn't turn up at all.
Then there were others like Claudius who just enjoyed it a bit too much.
He used to like looking at the expressions on the faces of the dying gladiators.
Others also didn't get involved enough.
Domitian liked to sit in his box, but he spent most of his time chatting to a dwarf in a red cloak.
Then there was Nero who went too far
and actually became the star of the show himself and performed as a musician.
So for emperors,
the games were a time when they had to get the balance right
between participation and maintaining their dignity.
But keeping the Romans in Rome happy and docile
was only one part of the challenge of running the Empire.
What about the 59 million other citizens and subjects of Rome scattered over its vast territories?
To keep them in their place as compliant, tax-paying units,
emperors depended upon the loyalty and commitment of local elites.
It was they, in thousands of towns large and small, that really ran the Roman Empire,
extracting revenues, building public works
and keeping order by imitating the bread and circuses programme developed in the capital.
The system was remarkably efficient and streamlined.
The whole of the Empire was administered by just 10,000 of these bureaucrats.
Modern Britain has half a million.
To cultivate and maintain their loyalty,
they were granted full citizen rights and generous tax concessions.
And perhaps most importantly, there was the imperial cult,
which turned emperors and their families into gods.
Here the emperor Antoninus Pius is being elevated to the heavens on the wings of an eagle.
In Ephesus in Turkey, the divine Hadrian had his own temple.
The members of Augustus's dynasty were worshipped here in Nimes in France.
This bronze statue behind me is of the emperor Claudius.
It comes from the temple of Augustus at Herculaneum in southern Italy.
The imperial cult wasn't just about religion, it was also about political control.
The problem that the emperor had was how to connect with his millions of subjects over a huge empire,
people he was never going to meet personally.
The imperial cult acted as a kind of hologram, beaming the emperor right across his vast empire
and allowing him to create some kind of personal connection with his subjects.
But when it came to religion, the Romans were not fundamentalists.
Here at the temple of Luxor in Egypt, it was perfectly acceptable
to worship the ancient Egyptian gods,
alongside the deified emperors of the imperial cult.
Elsewhere in the Empire, there was plenty of other evidence for Rome's religious tolerance.
We're here in the Bekaa Valley in Lebanon in what was once Heliopolis, the city of the sun.
A little bit of Rome from Rome.
Before it was called Heliopolis,
this was known as the Phoenician city of Baal-bek, dedicated to the god Baal.
Alexander Greekified the name but the Romans, when they took control,
preferred to keep things as they were.
Imperial Rome was just not interested in name changes,
preferring instead to add new labels rather than erasing the old.
In spiritual matters, the Empire was a sponge,
absorbing foreign gods as readily as it had gobbled up foreign territory.
This was the Temple of Jupiter,
but the Jupiter worshipped here was also understood to be Ba'al-Hadad,
a local storm deity who had been honoured here for centuries before the first togas arrived.
The Temple of Venus over there was also the Temple of Astarte, the Phoenician goddess of love.
And at the Temple of Bacchus, the wine god, it was also possible
to pray to Dionysius, an ancient eastern fertility deity.
The Romans were big tent polytheists.
All were welcome to local and traditional gods, just as long as they were willing to offer up
a pinch of incense to the imperial cult.
Rome tolerated everything, except for rebellion, political disorder and the non-payment of taxes.
For a region that had known the scourge of war in the past,
that must have sounded like a pretty good deal.
But the ironic truth about the Roman Empire was this -
the further you were from the toxic centre that Rome was becoming,
the more the stability and security created by the Pax Romana
could be enjoyed and exploited.
In the second century AD, where I'm standing now would have been on the very edge of the Roman Empire.
This way lies Rome - 1,500 miles
as the imperial eagle flies.
And this way lies Mesopotamia,
Persia, India, China...
and the very edges of the known world.
When we talk about the edge of empire,
we tend to think of Hadrian's famous wall clambering over the rain-soaked hills of Cumbria and Northumberland,
manned by homesick squaddies grumbling about their chilblains.
Well, here there was no wall or chilblains.
This was Palmyra, the queen of the desert,
and it tells a very different story of what life could be like under the Pax Romana.
Rome had acquired this desert territory during the last decades of the republic,
and Palmyra was first garrisoned during the reign of Augustus.
Even then it was a vital link in the east-west trade route,
providing an essential stop-over point between the upper waters of the Euphrates
and the Mediterranean coast.
For the Palmyreans, the arrival of the Romans
simply meant that a whole new market opportunity had opened up.
From the workshops and factories of Rome, supplies of manufactured goods.
From India and the east, spices and silk.
Of course we've met these people before - the Bronze Age merchants travelling with their mule trains
from Assur to Anatolia,
the Iron Age Phoenicians criss-crossing the Mediterranean with their sturdy ships.
Well, they're here too in Palmyra, the essential middlemen,
stitching together the political map of the ancient world with the thread of trade.
And as the Assyrians had their mules and the Phoenicians had their ships,
so the Palmyreans had their favoured mode of transport - the camel.
By mastering the art of crossing the desert with their camel trains,
the Palmyreans were able to join together what nature had put asunder.
But like all traders, what the Palmyreans needed most was peace and stability,
reliable supplies of stock and stable markets,
so that they could pursue their ultimate objective of getting rich quick.
This wasn't always easy.
To the immediate east of them lay the kingdom of Parthia,
a thorn in the side of Rome for centuries.
Like others before him, the Emperor Trajan decided to solve Rome's eastern problems once and for all.
He led his legions into Parthia and then beyond to the ancient cities of Mesopotamia,
following in the footsteps of Alexander the Great.
But whereas Alexander's victories had fuelled an appetite for further glory,
Trajan came to a rather different conclusion.
"This country is so immeasurably vast and separated from Rome
"by such an incalculable distance, we cannot possibly administer it."
He then turned round and went back west.
That was AD 117, and if you wanted to date the high-water mark of the Roman Empire,
then Trajan's rather world-weary conclusion would arguably be it.
Under Trajan's successor Hadrian, Rome reverted to a policy of peace with its eastern neighbours.
After 500 years of expansion, Rome finally decided enough was enough.
Fuzzy borders became lines in the sand
and Palmyra, on the critical interface
between the Roman and the non-Roman world, became a free city.
And that was when the good times really began to roll.
Some time in the second century AD and for around 150 years afterwards,
the Palmyreans achieved the perfect formula for their relationship with Rome.
First of all, they were important because they provided Rome
with something it wanted - spices and silks.
Second, there was no conflict of interest here
because the Palmyreans were only interested in profits,
whereas Rome, like all empires, was obsessed with its own destiny.
Finally, and best of all, the Palmyreans were far enough away from Rome
to be left alone to get on with it.
And today we can see the virtues of being left alone in the elaborate mausoleums
put up by some of the leading families of Palmyra
both above ground and under ground.
Memorials to their wealth and status,
but also to the benefits of being in the Empire rather than of the Empire.
But it wasn't just merchant princes who enjoyed the benefits of empire.
The ancient Greeks always used to say
that the basis for any successful society was eunomia - good order.
And that's what you can sense
in a set of remarkable archaeological finds from some of Rome's Egyptian cities,
the banal blessings of good order writ large.
As any private eye will tell you, what people throw away
is often more revealing than what they keep and cherish.
It was certainly the case here in the Roman city of Antinopolis
where, amongst the tons of broken pottery,
archaeologists struck gold - papyri, thousands and thousands of them,
so many that it's going to take generations of scholars to decipher and publish them all.
This wealth of written material allows us to reconstruct
in minute detail what life was like here in the heyday of the Empire.
Most of it is the ancient equivalent of those mountains of paper that clog up our lives today -
bills, tax returns,
personal letters, invitations, certificates,
contracts, to-do lists.
The kind of stuff that's either too important to throw away or too trivial to be bothered with.
From the nearby city of Oxyrinchus comes more of the same.
This one addresses the serious problem
of donkeys being driven too quickly through the busy streets of the city.
And this little note was written by two friends, Apion and Epimas,
to a schoolmate of theirs, Epaphroditos.
It contains the most extraordinary suggestion.
"If you let us bugger you and it's OK with you, we shall stop thrashing you."
And there's even a helpful little illustration here,
so Epaphroditos knew exactly what was expected of him.
And then there's this, a letter by Diogenes to one of his employees.
"A thousand times I've written to you to cut down the vines at Pahia.
"But today again I get a letter from you asking what should be done, to which I reply cut them down,
"cut them down, cut them down, cut them down, and cut them down!
"There. I say it again and again."
Go on, Diogenes. Why don't you say exactly what you mean?
But there's a twist to this tale of hot-rod donkey riders, smutty teenagers and slow-witted servants
and it suggests that the people of Antinopolis and Oxyrhynchus had other things on their minds.
You could say that these concerns presage the decline and fall of the Roman Empire.
Amongst the charming trivia, archaeologists also found this rather different text.
"The kingdom is inside of you and it is outside of you.
"When you come to know yourselves, when you will become known,
"you will realise that it is you who are the sons of the living Father.
"But if you will not know yourselves, you dwell in poverty and it is you who are that poverty."
These words are from the apocryphal gospel of St Thomas,
from which three extracts have been found amongst the bills and the junk mail.
What it shows is that alongside the everyday concerns about donkeys and vines,
there were people here grappling with profound and unsettling questions
about the meaning of life and the fate of their immortal souls.
Questions which the Roman Empire, despite its material wealth, was simply unable to answer.
In many ways, the Roman Empire represents the zenith of ancient civilisation.
Its values had taken root throughout its far-flung territories,
but its inability to address the spiritual anxieties of its subjects would prove to be a fatal flaw.
This weakness would be exposed and exploited by an obscure Jewish sect begun in the Roman province of Judea
with the execution of an unorthodox religious leader called Yeshua benYosef.
Christianity would go on to become
the official religion of Rome and a major contributor to its downfall.
The cult's extraordinary growth began after the Jewish revolt of 66AD
and the destruction of the High Temple in Jerusalem by Titus, the son of the Roman Emperor Vespasian.
This triumphal arch was built to commemorate
Titus's suppression of the Jews and inside it there are two friezes.
On one side, we have the emperor flanked by the winged goddess Victory
in his chariot and surrounded by his troops.
On the other, we have the spoils of victory,
the most sacred objects from the temple on the Mount, the menorah and the silver trumpets amongst them.
This art was as much about issuing a severe warning of the dangers
of resisting the Pax Romana as it was about tasting the sweetness of victory.
What the Romans actually did was sow the seeds of their later problems.
After the failed revolt, Jews dispersed throughout the Mediterranean world,
carrying with them the beliefs of Christianity.
These beliefs put Christians on a collision course with Rome.
They were fiercely monotheistic and balked at the imperial cult.
They made a sharp distinction between the sacred and the secular
and they looked forward to a glorious life after death,
making a mockery of the Empire's worldly devotion to the here and now.
Christianity initially took root away from the imperial centre
in places like Carthage in North Africa.
For the authorities here, to be a Christian was to be a revolutionary
and a target for persecution.
A new word would enter the religious lexicon - martyr.
The problem for the Romans was that for the Christians, martyrdom was a privilege not a punishment.
After all, it offered a guaranteed pass into the kingdom of heaven.
In Carthage, in 203AD, the amphitheatre here was the site of a notorious killing of Christians.
Worryingly for the authorities,
one of the female victims, Perpetua, came from one of the city's elite families.
Perpetua had been arrested with a group of other Christians including her pregnant servant Felicitas.
Both women refused to renounce their faith and both were sentenced to die in the amphitheatre,
even though just two days before the execution, Felicitas gave birth to a baby daughter.
Felicitas and Perpetua were brought up naked into the arena
and the crowd immediately started shouting for them to be sent down below again,
not because they wanted to show them mercy but because they felt squeamish
about Felicitas's lactating breasts which were dripping milk all over the arena floor.
When they were sent up again, they were fully clothed.
They were whipped and then a wild cow was sent into the arena to trample them.
But even after that, they were still alive and swordsmen were sent into the arena to finish them off.
The swordsman who was sent in to kill Perpetua, his hands were
shaking so much that she had to hold them so he could cut her throat.
Perpetua had got what she wanted - a martyr's death.
This bloody ritual would be repeated sporadically
in amphitheatres across the Roman Empire over the next century.
But persecution was never a coherent policy,
and when the Roman authorities abandoned it, frustrated martyrs
had to find other ways to express their rejection of the Roman world.
If it couldn't be achieved quickly through the executioner's blade,
salvation would have to be earned the hard way through extreme asceticism.
This is the world's oldest Christian monastery,
St Anthony's in Egypt.
Anthony was born into a wealthy Egyptian family, around 250AD.
At the age of 34, he decided to renounce his material possessions and dedicate his life to God,
so he headed into the desert to live the life of a hermit in a cave.
Father Demian, how many steps are there up to the cave of St Anthony?
I think maybe 1,300.
It is like the way to the heaven.
Is very long way and very tough way, but when you reach there,
you will get the prize.
So now we are arrived.
Here is our treasure, actually. This is the real monastery, I believe.
This is the cave of St Anthony.
He used to live here.
I believe that his blessing is still present inside the cave.
Just go and have...
Thank you very much, Father. OK.
Christianity was particularly attractive to those who wanted
to opt out from the comfortable certainties of the imperial system.
They wanted spiritual rather than material enrichment.
For these young men and women, asceticism offered an escape
from the straitjacket of private enterprise, public service and family commitment,
whilst at the same time, offering a blueprint for a new life,
one of poverty, abstinence, charity and penance.
For them, all the achievements of the Pax Romana, the laws,
the aqueducts, the peace and the prosperity were essentially meaningless.
But it's hard to see how a small, isolated group of gentle ascetics, with their eyes fervently focused
on the promise of a world to come, could be a problem to the mighty Roman Empire.
Well, for a start, Perpetua in Carthage, Anthony in Egypt
and the thousands who followed their example
were precisely the kind of wealthy, educated people
who would have been expected to take up active roles in the running and administration of the Empire.
By dropping out, they sapped the energies of a system
that ultimately depended on the active commitment of its elites
to keep the machinery of empire ticking over.
But it would take something far more radical
to turn this revolutionary movement into a force to be reckoned with.
The spiritual restlessness that drove some to martyrdom
and others to the desert went to the very top of the imperial system.
This is Constantine - the man who would turn a pagan empire into a Christian one.
He was a man of action rather than a man of faith.
But even he seems to have been looking for answers that his civilisation couldn't supply.
Constantine was actually quite promiscuous
when it came to one-to-one relationships with individual gods.
By the time he got to Christianity, he'd already been through Apollo and the sun god, Sol Invictus.
But his relationship with Christianity would endure.
It was possibly because Christianity's monotheistic tendencies
fitted very well with a man who had ultimately been responsible for the collapse of the Tetrarchy.
One emperor, one god.
The Tetrarchy had involved the carving up of the Empire between four different emperors.
It had been created by the emperor Diocletian at the end of the 3rd century AD.
The Empire had become too large and unwieldy for one man to rule.
But, after Dioletian's death, the rival emperors inevitably went to war.
This climaxed in 312AD at the Battle of the Milvian Bridge on the outskirts of Rome,
where Constantine defeated his rival, Maxentius...
..who drowned in the Tiber.
Christians travelling with Constantine's army
were quick to attribute the victory, commemorated on this arch,
to the divine favour of their god.
Constantine always ready to give a god the benefit of the doubt,
showed his gratitude a year later by passing an edict of toleration
granting Christians freedom of worship throughout the Empire.
A decade later, when Constantine emerged as sole emperor,
the obscure Messianic cult from Judea really came in from the cold.
Constantine demonstrated his commitment to Christianity with hard cash.
He endowed a series of magnificent churches,
including St Peter's Basilica in Rome
and the Church of the Holy Sepulchre in Jerusalem,
which was built on the supposed site of the Son of God's tomb
on the orders of Constantine's pious mother, Helena.
These would become new centres of political, as well as spiritual power, in Constantine's empire.
In return for political support and generous patronage,
Constantine expected one thing above all from his church -
a consistent message on Christianity's core beliefs.
The Council of Nicaea, held in 325AD in present-day Turkey,
was the first and most famous attempt
by the Christian establishment to get its story straight.
As you can see, there's not much left of the place where the First Council of Nicaea was held.
But, although the bricks and mortar are long gone,
the legacy of the meeting of bishops that took place in 325AD has endured
because it was here that the Rome of Romulus and the Republic and Augustus Caesar and the Empire
began to make way for a new Rome - a Rome of priests, Popes and the Holy Catholic and Apostolic Church.
Constantine presented the council with what seemed like a reasonable request -
a firm date for Easter and agreement on the precise nature
of the relationship that stood at the heart of Christian faith -
that between the father, the son and the holy ghost.
Easier asked than answered.
These seats were used for a much later council of Nicaea
which was held here in the church of Hagia Sophia centuries after the first one.
But I don't suppose the seating technology had changed very much.
And the point of this is that these seats are incredibly cramped and uncomfortable.
Every time you sat down, they must have served as in invitation to come up with a quick compromise.
And that's exactly what Constantine wanted - a quick political fix
to what he said were nothing more than small and trifling matters.
What he didn't appreciate was that this was a new type of politics - a politics of faith.
In this new political landscape, nothing was small or trifling.
The bishops ended up compromising on a form of words familiar to all Christians today.
We believe in one God, the Father Almighty, and in one Lord Jesus Christ, Son of God
and begotten of the Father, and in the Holy Ghost.
Constantine was not finished yet.
He made a decision that effectively brought to an end 500 years of Roman history.
On 11th May 330,
Rome was finally eclipsed the capital of the Roman Empire.
Of course, there had been contenders before, but this time it was for real.
500 miles east of Rome, in the Straits of the Bosphorus,
Constantine founded the city of Constantinople.
He planned it to be nothing less than the new Rome.
Constantine based himself in Constantinople -
present-day Istanbul -
until he died in 337AD,
when he was finally baptised on his death bed.
CHURCH BELL TOLLS
With just one exception, Constantine's successors
would follow his example and be Christians.
Their support made the church a real power in the land
and towards the end of the 4th century AD,
it began to assert its independence on its imperial patrons.
The main driving force on the Christian side was Ambrose, Bishop of Milan.
A clever and energetic man - he was clearly unfazed with dealing with emperors.
Before he joined the church, Ambrose had had a successful career as a senator and governor.
Ambrose was firmly of the belief that it was the Christian Church
and not the Roman Emperor who was God's main representative on Earth.
This position was bound to set him on a collision course
with emperors who were used, by this time, in intervening in religious affairs whenever they felt like it.
The scene was now set for a dramatic and very public showdown here in imperial Milan.
It pitted Ambrose against the Emperor Theodosius -
a battle-hardened campaigner, but also a pious Christian.
The spark was the massacre of 7,000 rebellious subjects
under the orders of Theodosius in Thessaloniki in Greece.
Many of the victims were Christians and Ambrose felt compelled to respond.
He banned Thedosius from the congregation in his cathedral
and threatened him with excommunication if he didn't repent.
Theodosius took the hint and, for the next couple of months,
the citizens of Milan were treated to the extraordinary spectacle of their emperor - the most powerful
and feared man in the Roman world - doing acts of public penance, stripped of his imperial insignia.
And when eventually the chastened emperor was readmitted back into the Catholic fold,
Ambrose insisted that he stood with the congregation rather than joining the priests in the sacred sanctuary.
Ambrose had emphatically and literally put Theodosius in his place.
Ambrose's spectacular humiliation of the emperor impressed ambitious men about where real power now lay.
One of these men was a brilliant scholar called Augustine.
Baptised here in Milan by Ambrose himself.
Augustine had been born into a relatively prosperous family
in North Africa and, after a good education in Carthage, had landed a professorship here in Milan.
But after being baptised, he decided to return home and devote himself to God.
This was a decision that would not only change his life
but also the whole course of Western Christianity.
Augustine returned to Africa,
intending to follow the example of St Anthony,
leading a simple, monastic life.
But his plans were changed for him when he visited Hippo Regius,
a port city on the North African coast.
When he worshipped at the church here, he soon got noticed.
With his classical education and oratorical skills, the congregation urged him to stay on, which he did,
and, eventually, he would become their bishop.
Augustine was soon playing an active part in the religious battles
that raged, using pulpit and pen to attack pagans and heretics alike.
He'd been bishop for 15 years when history gave him a controversy that he could really get his teeth into.
In the late summer of 410, shocking news reached Hippo Regius.
Rome, the founding capital of the greatest empire
history had ever known, had fallen to Alaric and his Visigoth army.
Three days of looting followed
and many of Rome's finest buildings were destroyed.
The mausoleum of the great Augustus was ransacked,
burial urns were overturned and the ashes of Roman emperors were scattered on the streets.
Rome may have been stripped of its pre-eminence by Constantine,
but it still retained a symbolic importance
and its fall to German Barbarians sent reverberations throughout the Empire.
In the weeks and months that followed, Hippo filled with traumatised refugees from Rome.
They wanted to know why the mother city had fallen.
Augustine took up his pen and gave them an answer.
He wrote a blistering attack on the myth and mystique of Rome,
writing a Christian counter-history of the city, a no-holds barred decline and fall
from the city's virtuous founders to the decadent, selfish, materialistic citizens of his own day.
If Rome fell, Augustine argued, it was because it deserved to.
In his coup de grace, Augustine attacked the very ideals
that Rome, and indeed all the great civilisations of the ancient world, aspired to.
These earthly cities were doomed to fail because they were the work of corrupt mankind.
It took Augustine 13 years to finish his masterpiece - The City of God.
And, for me, there are few bleaker assessments of the futility of civilisation-building.
For Augustine, no purpose or meaning could be found in the earthly city,
only the city of God offered these and that could only be reached beyond the grave.
Until that glorious release, the righteous man should act
like a pilgrim in the fallen world of mankind,
taking advantage of the peace and security that civilisation offered
but without ever mistaking it for anything substantial or enduring.
The good man was just passing through,
and the great technological, political and cultural achievements of civilisation
were mere stepping stones to the eternal glory of the City of God.
It's been 1,500 years now since the City of God took on the city of man
and, in that time, other prophets from other religions have added their voices of criticism.
But despite its manifold and serial failures, the city of man has endured.
Elaborate schemes for political reform, social justice or national greatness have been tried and tested
often to destruction.
And, in the darkest days, many of which have fallen in our own times,
the very idea of civilisation has been called into question.
But despite all the calamities, crises and dead-ends,
we've returned again and again to the possibilities offered by the city of man,
hoping to get it right next time.
There's no going back to the comforting securities of family, kin and tribe.
Civilisation has transformed us into a species
which, for better or worse, chooses to live with strangers.
And we need to keep on trying to find ways of making that unlikely choice work.
Personally, I'm optimistic.
Homo sapiens, they say, has been around for at least 160,000 years.
The city for less than 6,000.
So it's early days yet.
We must keep the faith and try and make it work.